Hi Dongjiu, On Tue, Jul 04, 2017 at 03:04:54PM +0800, gengdongjiu wrote: > Hi Christoffer, > > On 2017/7/3 16:21, Christoffer Dall wrote: > > On Mon, Jun 26, 2017 at 08:45:43PM +0800, Dongjiu Geng wrote: > >> Handle userspace's detection for RAS extension, because sometimes > >> the userspace needs to know the CPU's capacity > > > > Why? Can you please provide some more rationale. > > userspace mainly want to know whether CPU has RAS extension capability to decide whether need to specify the syndrome value. > if have, userspace specify the syndrome value. otherwise, not specify the value. > > James ever suggest not want userspace to know the capability, and let KVM to judge the RAS extension capability. > > but I consider it again, userspace know the RAS extension capability may be better, which can avoid KVM return error if > CPU does not support RAS extension. So first of all, while I appreciate your efforts to explain your rationale here, I am also asking you to provide a more comprehensive commit message for the next version of the patch. > > could you give me some suggestion that whether let userspace to know the RAS extension capability? > I haven't thought much about it, but there are unanswered questions to me. For example, does the type and capabilities of the guest in any way affect whether or not this features should be available? Are there any concerns with respect to migration? And then the point I raised below, which is that this KVM-specific ioctl is returning a hardware property of the CPU (the one the ioctl happens to run on - what happens on a heterogeneous system?), but not really what KVM can and cannot do. At the very least this should be based on a more generic in-kernel functionality, which reports the capabilities of a system to KVM, and KVM could then tell userspace if it has a certain capability. Hope this helps, -Christoffer -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
